Due to recent technical innovations, ink jet recording apparatuses, which accomplish image recording by ejecting minute ink droplets onto a recording surface, have been capable of achieving high image quality approaching conventional silver salt photography, as well as of reducing apparatus cost. As a result, variations of the ink jet recording apparatuses have increasingly been introduced onto the market.
Such ink jet recording apparatuses are constituted in such a manner that image recording is accomplished by ejecting minute ink droplets. As a result, in order to produce higher image quality prints, it is essential that ink droplets be properly ejected onto specified positions. Accordingly, based on such reasons, it has been required that recording be carried out while minimizing the distance between the printing head and the recording medium.
However, the components of recording media, employed in such ink jet recording apparatuses, are mainly comprised of paper materials. As a result, the recording media result in curl, which has occasionally caused problems in which the recording medium comes into contact with the printing head of the ink jet recording apparatus.
As noted above, when, due to the formation of curl, the recording medium comes into contact with the printing head of the ink jet recording apparatus, it becomes impossible to satisfy the essential condition, “to properly eject ink droplets onto the specified positions”, resulting in degradation of the image quality of printed images. Further, the contact of the printing head results in abrasion as well as staining on the recording surface of the recording medium, and in the worst case, so-called paper jam occurs in which the recording media are jammed in the interior of the apparatus.
Particularly, when the recording medium is wound into a roll, the magnitude of curl of the recording medium is enhanced due to its roll-set curl. As a result, problems due to contact of the recording medium with the printing head of the ink jet recording apparatus have become more serious.
In order to overcome the contact problems, even though the recording medium is arranged so as to keep it a suitable distance from the printing head of the ink jet recording apparatus, the magnitude of the curl varies depending on properties of the recording medium. Further, when the recording medium is wound into a roll, the magnitude of the curl also varies while unwinding the recording medium. As a result, it has been difficult to arrange the recording medium so as to keep the desired distance from the printing head of the ink jet recording apparatus.
Even after the aforesaid recording media are ejected from the ink jet recording apparatus, problems have occurred in which ejected recording media, when they exhibit curl, are not stacked well on the ejection tray. Still further, problems have occurred in which it is difficult to introduce recording media, which exhibit the tendency of curl, onto the market as a commercially viable product.
On the other hand, in recent years, high image quality, as well as high speed printing, has been demanded for ink jet recording. In order to meet such demands, ink jet recording media are desired which increase ink absorption amount as well as ink absorption rate, and improve glossiness.
Based on the structure of the ink absorptive layer, ink jet recording media are divided mainly into two types. One is an ink jet recording medium comprising a swelling type ink absorptive layer. The medium exhibits desired glossiness, but exhibits a low ink absorption rate. As a result, the resultant image quality is degraded due to color bleeding or beading.
The other type is a porous type ink jet recording medium comprising an ink absorptive layer comprised of a porous layer which is comprised of a small amount of water-soluble binders and crosslinking agents as well as a large amount of inorganic pigments. The medium results in high image quality due to a high ink absorption rate. However, when placed in low humidity ambience, image quality is degraded due to the formation of fine cracks on the surface of the recording medium.
It is possible to form a stable layer by increasing the amount of water-soluble binders or water absorptive resins which are employed in these ink jet recording media. However, when a large amount of the water-soluble resins are employed, the volume of the water-soluble resins varies due to the variation of ambient conditions, and mainly due to the variation of humidity due to swelling and contraction of the resins themselves. As a result, the recording media exhibit curling.
Even though variation due to ambience is minimized by adding fine resinous particles instead of water-soluble binders employed in these ink absorptive layers, irregularity is partially formed immediately after ink absorption when recorded upon employing water based ink.
Specifically, in the case of so-called RC paper which is prepared by coating resins onto both sides of the paper employed as a base material of the recording media, the volume variation due to the base material is relatively small depending on the variation of the ambience. As a result, the difference in the swelling ratio between the ink absorptive layer side and the base material side increases and the tendency to curl increases.
Further, instead of paper sheets, roll paper has increasingly been needed for continuous image production at large runs. Recently, roll recording media have been employed not only for commercial printers (large format printers) but also for personal use printers.
From the viewpoint of the ease of handling as well as decrease in apparatus size, roll recording media, which are wound onto a relatively small diameter core, are demanded. Thus, in the roll recording media, curl is present prior to printing, irrespective of ambient conditions.
When image recording is carried out with a ink jet method onto such a recording medium exhibiting inherent curl, as is described above, during recording, printing quality is degraded due to contact of the recording medium with a printing head as well as variation of the distance between the recording medium and the printing head. Further, after printing, when curl, as well as partial irregularity, remains, image quality is degraded and problems occur when printed media are placed in picture frames or stored in bags. Further, when printed media are adhered onto a wall without any treatment, some part of image may not be visible. When a great magnitude of curl is manually corrected, some part of image may occasionally be damaged.